Abstract

THE EFFECT OF INCREASING LEVELS OF EXERTION ON KNEE JOINT PROPRIOCEPTIONWilliam S. Gear, PhDUNIVERSITY OF PITTSBURGH, 2004The purpose of this study was to examine the effect of incremental levels of isokinetic concentric muscle exertion on passive reproduction of passive positioning (PRPP) and active reproduction of passive positioning (ARPP) at the knee joint in male and female collegiate soccer and basketball players.Subjects for this study included 20 (10 males and 10 females) volunteers. Subjects performed knee extension and flexion concentric isokinetic exercise until torque output fell below the 10%, 30%, or 50% of maximum hamstring torque for three consecutive repetitions. Subjects were then tested on either PRPP or ARPP following the isokinetic exercise session. Following testing of the first independent measure, subjects were given a 20 minute rest period. Following the rest period, the procedure was repeated for two more exercise sessions. Testing of PRPP and ARRP was counterbalanced between trials and sessions in order to decrease the chance of a learning effect on the results of each testing session.The major findings of this study indicate that increasing levels of exertion do not have a significant effect on either active reproduction ability [ARPP-45 degrees (F2,38 = 0.88, p = 0.42), ARPP-30 degrees (F2,38 = 0.69, p = .51), and ARPP-15 (F2,38 = .23, p = 0.80) or passive reproduction ability [PRPP-60 degrees*s-1 (F2,38 = 0.25, p = .78) , PRPP-90 degrees*s-1 (F2,38 = 0.31, p = 0.73), and PRPP120 degress*s-1 (F2,38 = 1.58, p = 0.22)]. However, the reliability of all PRPP and ARPP measures at 15 degrees demonstrated poor reliability.Fatigue has long been theorized to be a contributing factor in decreased proprioceptive acuity, and therefore a contributing factor to joint injury. The lack of significant findings may be explained by the idea that as the level of muscle fatigue increases muscle spindle discharge increases. Poor reliability for all PRPP and ARPP at 15 degrees draws into question the meaningfulness of the results for these measures.